A plastic magazine and trigger, which could have potentially been fitted together to make a gun, were seized by police in Manchester along with the 3D printer that created them.
The components are now being examined to see if they could have been fitted together to make a viable 3D gun.
The technology works by allowing anyone with a 3D printer - which can be bought on the high street for £1,200 - to download designs for guns or components.
A man has been arrested on suspicion of making gunpowder and remains in custody for questioning, Greater Manchester Police said.
More top news
Weather set to stay cool and cloudy tomorrow
The multi-millionaire strip-club owner defended his policy of taking 23% of the service charges made by waitresses in his bars.
Eleven years after her arrival at Animal Lifeline centre in Staffordshire, Maggie is still waiting for a new owner.